The present invention relates to a bobbin-changing device for a textile winding machine in which an elongate filamentary member, more specifically a thread or strip, composed of textile fibres is wound on successive bobbins, the device being for replacing a fully wound bobbin with an empty bobbin, and including means for allowing the fully wound bobbin to drop down from its winding position and automatic means for severing the thread or strip near the periphery of the fully wound bobbin so that the new leading end of the thread or strip can be passed to an empty bobbin.
The invention is particularly, but not exclusively, applicable to the winding machine (normally termed a winding frame) of a high draft or attenuation drafting frame, but in general, the thread can be any spun yarn of preferably discontinuous textile fibres, or the strip can be a sliver or a roving. The rotary member on which the thread or strip is wound is termed herein a bobbin, but the term bobbin is used to include any suitable rotary member. In the art, the fully wound bobbin may be referred to as a reel.
Normal practice for severing the thread or strip is to cut the thread or strip, and British Patent Specification No. 1,308,842 discloses one prior cutting means.
A disadvantage of the use of cutting means is that the cutting means must be resharpened from time to time, and it is also difficult to insert the cutting means between the bobbin and the drive roll (the member which engages the periphery of the bobbin and causes it to rotate) in such a way that the thread or strip is cut close to the bobbin so as to leave a reasonably long leading end for attachment to the empty bobbin.
However, automatic means have been proposed for severing or breaking the thread or strip solely by applying excessive tension thereto, i.e. without the use of any cutting means for severing the thread or strip. The elimination of the cutting means avoids any necessity for resharpening, and it is found that the thread or strip can be broken at or very close to the periphery of the fully wound bobbin, leaving a new end which is as long as possible. No extra member need be brought into contact with the thread or strip, the extra friction where the thread or strip passes over the drive roll (which is used in most textile winding machines) ensuring that the thread or strip is broken between the drive roll and the periphery of the fully wound bobbin.
In one such proposal, the fully wound bobbin is dropped down so quickly that the position at which the thread or strip reaches the periphery of the fully wound bobbin moves faster than the delivery of the thread or strip. However, the fully wound bobbin is a heavy object, and the device must be especially strong subsequently to stop the falling bobbin, or a special decelerating arrangement must be incorporated, both of which alternatives make the device more expensive.
In another proposal, the rotation of the bobbin is speeded up for a short period, thereby accelerating in the winding on direction the position at which the thread or strip reaches the periphery of the fully wound bobbin. This proposal involves the incorporation of a special transmission, for example a change speed gear box, in the drive to drive the roll, making the arrangement significantly more expensive.
It is an object of this invention to simplify the automatic breaking means and to avoid increasing the kinetic energy of the fully wound bobbin over that attained during normal drop-down after winding.